Bring a large saucepan of salted water to a boil over high heat. Cook beans in batches until tender. Remove from the water and stop the cooking by placing in a bowl of ice water. Drain and reserve.
To make the soffrito, combine the onions, red pepper and olive oil in a small skillet with a pinch of salt. Place over medium heat and cook until vegetables have cooked down and are soft, about thirty minutes serving occasionally.
To serve, heat a large skillet over high heat. Add the soffrito to the pan and the beans. Toss beans with the soffrito and season with salt and pepper to taste. Serve alongside of a piece of grilled meat or fish.